This application claims the priority of Japanese Patent Application No. 2000-68383 filed on Mar. 13, 2000 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an endoscope, and more specifically to a device capable of observing an object by optically enlarging the image of the object.
2. Description of the Prior Art
Recently, an endoscope (electronic endoscope), etc. has been provided with a movable lens for variable power in an objective system of a scope tip, the movable lens is driven by an actuator, etc. so that an image of the object can be optically enlarged. The optically enlarged image is captured by a solid-state image pickup device such as a CCD (charge coupled device), etc., and an enlarged image of the object is displayed on the monitor by performing various image processes by a processor device on a video signal (image signal) output from the CCD. In the above mentioned optically variable power mechanism, a target portion can be observed by enlarging the image of the portion for the magnification of 70 through 100.
In the optically variable power function of the above mentioned endoscope, an encoder, etc. is mounted to detect the moving position of a movable lens for variable power. That is, a correct value of magnification can be obtained by the encoder detecting the position in the optical axis direction of the movable lens moving by a drive mechanism.
However, the above mentioned movable lens is built in the optical objective system of the thin tip of the endoscope. If the encoder for detecting the position is also built in the tip, the diameter of the thin tip is necessarily larger.
The present invention has been developed to solve the above mentioned problems, and aims at providing an endoscope capable of detecting the moving position of a movable lens for variable power without an encoder, etc.
To attain the above mentioned purpose, the present invention includes a movable lens, provided at the tip of an endoscope, for observing an optically magnified image, a drive circuit for driving the movable lens, and a control circuit, which uses the moving time of the movable lens from a predetermined end as the variable power position information of the movable lens by measuring an entire moving time of the variable power movable lens moving between driving ends, for performing various controlling processes according to the variable power position information about the movable lens.
It is desired that the control circuit initializes the moving range of the movable lens when the first variable power switch is operated after electric power is applied.
The control circuit can also display the variable power position information specified by the moving time on the monitor.
With the above mentioned configuration, the entire moving time of the movable lens, for example, from the near end to the far end, for variable power is measured before a variable power operation. When a near switch is pressed, the decrement count value of the moving time from the far end is the position information about the movable lens. When a far switch is pressed, the increment count value is the position information. The entire moving time count is allotted to a predetermined stage to display the variable power position information, and the magnification (status) of an image is stepwise displayed on the monitor. Furthermore, the variable power position information is also used as the information as a notification that the movable lens is reaching the network and the far end. With the prediction of the approach to the ends, the reduction of a drive brake and a drive speed can be prevented.